1. Field of the Invention
The present invention relates to a control method and to a control device for a rotary valve-driven jigging machine for processing coal or other minerals, particularly for a rotary valve-driven throughput jigging machine whose pulse chambers are periodically charged with compressed air in order to generate a pulse motion and are disposed below the jigging screen.
2. Description of the Prior Art
With jigging machines for processing minerals, the lift of stroke, given a constant excitation intensity, depends on the thickness of the material layer lying on the jigging screen, particularly given throughput jigging machines which are pulsed from below. The cause lies in the attenuating influence of the minerals.
It is known from the German published application No. 25 39 374 to measure the layer height of the specifically heavier minerals given a jigging machine by means of a sensing element and, given an increase of the layer height, to increase the intensity of pulsation of the separating liquid. Such a control, however, depends greatly on the accuracy of the sampling of the layer height of the heavier minerals and is therefore inaccurate. Since there is an optimum lift of stroke for each grain size of the charging material, from which there should be no deviation given an unchanged grain size, the vitiation of the processing result can, under certain conditions, even occur by so doing.